If you decide on the more expensive model, you can bring this one back and pay the difference.如果你决定了更想要贵一点儿的那一款，你可以交回这个，补上差价就可以了。If you put all your savings towards the cost of a bike, your Dad and I will pay the difference.如果你用上了全部积蓄买自行车，那么差额由我和你爸来付。